Fit teenagers less likely to suffer from depression as adults

Embargoed until 14 June 2012

A study of more than a million Swedish men reveals that good
physical fitness at the age of 18 is associated with a reduced risk
of serious depression later in life.
The study was carried out by Swedish researchers, and is
published online today by the British Journal of
Psychiatry.

Previous studies have shown that a sedentary
lifestyle increases the risk of depression, but most of these have
been based on interviews with adults.

Researchers from the University of
Gothenburg’s Sahlgrenska Academy carried out a large-scale study of
all Swedish men born between 1950 and 1987, with no history of
mental illness, who were enlisted for mandatory military service at
the age of 18. When enlisting, all 1,117,292 men were given
extensive physical and psychological examinations, including tests
of their cardiovascular and muscular fitness.

The researchers followed up the men between
1969 and 2008, and used information from the Swedish National
Hospital Discharge Register to see how many had received inpatient
treatment for depression. They found that those who performed
poorly on the cardiovascular fitness tests at the age of 18 were at
greater risk of being hospitalised with depression in later
life.

Dr Maria Åberg, the researcher who led the
study, said: “The teenage years are a critical period in the
development of the brain, when higher functions are established and
social and emotional skills develop. Our study demonstrates that
low cardiovascular fitness at age 18 predicted serious depression
in adulthood.

“We performed separate analyses to reduce the
risk for possible reverse causation – in other words, the
possibility of early symptoms of depression at the time of
conscription affecting the men’s performance on the physical tests.
We also undertook a special analysis of the 389,000 men in the
study with one or more brothers, to rule out environmental and
hereditary factors. Even after taking this into account, the
association between physical fitness and risk of depression
remained. Even more remarkable is that the increase in risk of
depression could be observed in the men up to 40 years later.”

Dr Åberg and her research group have shown in
a previous study that high levels of fitness as a teenager impact
on IQ and academic performance, and she thinks that schools should
give sport a higher status and more resources.

Dr Åberg concluded: “While there’s a need for
more research in this area, our results provide strong support for
school curricula including more active sporting activity and
encouraging habits that build and maintain physical fitness.”